In recent years, with the increasing requirements on the display effect, the value of PPI (pixels per inch) of a liquid crystal display is increased continuously, so more pixels are needed to arrange in per unit area of the display screen, and correspondingly more wirings are needed. Accordingly, the capacitance and resistance among metal layers will be multiplied. Therefore, time delay and power dissipation become obvious, which will notably affect the usage of customers; moreover, it is contrary to the popular trend of energy conservation and environment protection nowadays. In order to decrease the capacitance between metal layers, it is needed to adopt a thicker insulating material with a lower dielectric constant. If the thickness of the inorganic insulating material prepared by CVD (chemical vapor deposition) method is increased, the requirements on production cost and process will become very high, and especially the technical problem brought by etching is hard to avoid. Meanwhile, the process time will be increased. So the yield will be affected to a large extent, and the competitive edge of an enterprise will be reduced. By contrast, selection of an organic insulating material brings about the obvious effects such as simple production process, lower cost, easy adjustment of thickness and decreased power dissipation. Meanwhile, the load of the common electrode is reduced and the undesirable greenish display will be improved.